1. Field of the Invention
The present invention relates to the structure of an inductor for mixed mode radio frequency (RF) integrated circuit devices, and more particularly to a vertical type inductor by using dual damascene process for mixed mode RF devices.
2. Description of the Prior Art
In recent years, for the brand new 0.18 um semiconductor process, there has been an increasing drive towards integrating high performance analog and digital circuitry on chip (mixed mode device). For the mixed mode radio frequency (RF) device, it needs to process the inductor on the electrical circuit. Current inductor is made by a horizontal aluminium-metal-line structure. The horizontal metal-line structure normally needs large area on chip. Especially, the resistance of aluminium is too high that leads the current small and the inductor performance impacted.
According to the above issue, normally a three-dimensional type structure is equivalent to a single-loop structure with a specific cross-section area that equals to the summation of cross-section area of each loop of the spiral structure. For a required inductance, the more loops inside the plane spiral structure the less area occupied by the plane spiral inductor. Therefore some disadvantages of the plane spiral structure are apparently observed, especially when the integrated circuit is highly integrated or the inductor is used by a radio frequency integrated circuit. The consumed space on the substrate by inductor is too large and the drawback is more obvious while integrated circuit is highly integrated or multilevel metallization is necessary.